Talk to your high school's administration office to see if they are partnered with any schools to offer dual enrollment courses on campus. These courses are usually the only dual enrollment option that allows students to earn high school and college credit at the same time. In most cases, students must take these classes separately either after school, online or over the summer.
Contact the university where you would like to attend college if your school does not have a partnership or does not offer any type of dual enrollment. A good place to start is at the college's website. Miami Dade College in Florida, for example, offers dual-enrollment courses to high school students independently. Students sign up for courses through the university and attend them outside of regular school hours.
Contact local community colleges, regarding their dual-enrollment courses. These schools are plentiful across the nation; one is likely to be within driving distance. They are more immersed in local communities and almost always have courses that provide college credit at the high-school level.
Research online colleges and their entry criteria. If you are planning to attend a specific college or university after high school, check with the administration office to see which accredited online schools (Kaplan, University of Phoenix and Ashford University, for example) are accepted for transfer credits.